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AF 447 Search to resume (part2)

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AF 447 Search to resume (part2)

Old 26th May 2011, 13:23
  #2441 (permalink)  
 
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Technology exists such that a pilot should never be in a position where he or she has to question the quality of primary air data. Air data systems on passenger A/C without the aforementioned should be rated VFR only IMHO.
Away for a couple of days and catching up, but the above just about sums up my gut feelings as well. This problem has been known about for years, with fwics, many examples of uas causing at very minimum, added crew workload and stress. I know change in aviation is glacial, but this problem should have been fixed as a regulatory requirement years ago.

Have been trying to think of a suitable analogy, so how about this:

Buying a new car from the showroom, salesman tells you how good and reliable the car is, but then tells you that when it's very cold, there's an intermittent fault that causes the headlights and instruments to fail. It usually only happens for a short period, but could cause a serious accident if the car is travelling at speed. The manufacturers have been trying to correct the fault for some time, but with no success. The advice is therefore, not to travel at more than 20mph at night. Does anyone think that such a vehicle would be allowed to be sold anywhere ?...

I think sometimes you need a sense of the surreal to put things into perspective...
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Old 26th May 2011, 13:25
  #2442 (permalink)  
 
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sensor_validation

Don't under-estimate Airbus engineers, 3 sensors, median filters, time delays are all included to minimize false alarms, but what is left is the remote possibility that any 2 may fail in exactly the same way at the same time - so check out the following, especially the 'foreign filing date Sep 23, 2009' :-

Quote:
United States Patent Application 20110071710 Kind Code A1 Puig; Stephane ; et al. March 24, 2011
METHOD AND DEVICE FOR DETECTING AN ERRONEOUS SPEED GENERATED BY AN AIR DATA INERTIAL REFERENCE SYSTEM
Well I agree that from Airbus engineers point of view double or triple Pitot's failure is a very low probability event. My university used to deal with "aircrafts" going out of the atmosphere and then back in, so Pitot's were one of the many sensors allowing computer to integrate positions and speed. And cross checking was a must. Remember this knowlege was around from 12 April 1961 and culminated by Russian space shuttle flown 100% by on-board computers.

Very sad that we paid such big price for engineering mistake or in fact "overseeing" the probability of failure being not so low. For example bird strike coud give the same result for all three tubes, since birds do fly in formations (flocks).
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Old 26th May 2011, 13:33
  #2443 (permalink)  
 
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Block pitots - back to basics

Thinking out loud....

Ok, so a pitot in it's simplest form is a tube facing into the 'liquid' flow, such that the resulting pressure can be measured with a transducer (diaphragm). At a constant (fixed) altitude that's all you need to measure 'speed' (once calibrated). However the measured pressure is a function of two components - there is a static component to the pressure (effectively due to the mass of the column of air pressing down on the diaphragm) and the dynamic component due to movement (effectively the additional pressure due to more air molecules pressing on the diaphragm). So if the thing that needs it's speed measured can change altitude, then we need to measure both dynamic and static pressure, and subtract the later from the former to derive speed irrespective of altitude. So far so good? (Please excuse the layman-esque language, but longer words make my head ache).

Alrighty then... so all's well and good until something blocks the dynamic tube - moisture, bees, ice, whatever - bad things happen.

Considering moisture - water - pretty common on Earth, so what's the solution - drain holes. Now this is where I need some help. Obviously the drain holes MUST be significantly smaller than the inlet port (otherwise there would be no pressure to measure - all the air would flow out the 'drain'...), so in normal operation we have air entering the inlet port and some portion of that flow exiting the drain? Clearly it is possible to calibrate the sensor to compensate for this, so the speed measurement still occurs.

However, block the inlet (ice), with the drain still open and the pressure will drop to static (indicated speed will decrease, at the limit to zero). My assumption is this is the failure mode we are discussing? (Since a blocked DRAIN alone will cause the speed to over-read).

My thought is this - in BOTH malfunction cases the flow inside the pitot has stopped at least through the drain - so why not include a mass-flow sensor right there in the drain outlet? Can we compare the GPS/INS derived speed to the pitot derived output and cross-check this with the mass-flow value, and figure out if we have a sensor problem? If our GPS ground speed is 400 knots and the pitot IAS is 80knots, with mass-flow derived value of 0 then there's a problem? I am presuming that pitot icing occurs fairly rapidly.

Am I oversimplifying?

- GY
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Old 26th May 2011, 13:42
  #2444 (permalink)  
 
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If you view an accident as a series of links in a chain, or a series of holes in slices of cheese - whichever one prefers - surely the elimination of any link, or hole, is a valuable goal. Granted, we do NOT know yet, but we obviously have good reason to believe that UAS was a contributing factor here. Yes, we could view that as something that "should" have been little more than another snag in the book for the makers of the pitot probes to ponder as they look toward eventual corrective actions... but the truth is, in this case, that may well have been a single link which, if it hadn't occurred, would have meant this conversation wouldn't be happening (and a ship load of trusting souls would still be alive!)

I know UAS alone should not have led to this result. ...but then, neither should a fuel leak in one engine have led to all tanks empty.... but it did, and the fuel leak should never have occurred. ...and, I feel just as strongly, airspeed indication should never be unreliable.

This one is serious of course, but how did it become that way? That has been the question from the beginning...how did this aircraft go from stable, M0.82 flight at FL350, to a pancake impact with the sea in less than six minutes?
Thankfully, very soon we'll know much more.

I hope I'm not getting under your skin.

Cheers,
3hl

Last edited by 3holelover; 26th May 2011 at 16:52.
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Old 26th May 2011, 13:59
  #2445 (permalink)  
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I like simple. Nomenclature is a challenge, it was ever so. On either side of an event, I see two bookends. One is "Proximal" cause, ie engine spool down, the other is "procuring cause", cold soaked fuel in China.

In between are fuel supply architecture, spar valve actions, low and high pressure pumps, SOPs, and a flawed design re: Heat exchanger and spill circuitry.

I have never liked the cheese hole theory, it makes me hungry and I get distracted.

I am one hundred per cent on board wih PJ2. When one says "It was not the pitots", one expects a little slack. Given the 17 year history of A330 and a "gazillion miles", and the unfortunate smoking gun of poor crisis management in dependability, by now, don't we know what we mean ?


 
Old 26th May 2011, 14:09
  #2446 (permalink)  
 
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Hi, jcjeant,
Originally Posted by jcjeant
Methink it was a know problem .....
Please, do not quote from any "sources" whithout also providing a link or a credit for your quotes. Also, in past posts, you should refrain from posting translated French press articles into English using auto-translation (everybody can do it himself, but the end result is most of the time meaningless).

Of course, one could certainly point that what you have posted above is far from an "objective" point of view about those probes issues but, as it seems to comfort you and few others into your Airbus consipiracy feelings, please, go ahead but you should certainly include the source where it comes from.
S~
Olivier

Last edited by takata; 26th May 2011 at 14:22.
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Old 26th May 2011, 14:20
  #2447 (permalink)  
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takata

"...Please, do not quote from any "sources" whithout also providing a link or a credit for your quotes. Also, in past posts, you should refrain from posting translated French press articles into English using auto-translation (everybody can do it himself, but the result is most of the time totally meaningless).

Of course, one could certainly point that what you have posted above is far from an "objective" point of view about those probes issues but, as it seems to comfort you and few others into your
Airbus consipiracy feelings, please, go ahead but you should include the source where it comes from.
S~
Olivier ...."



"Conspiracy" is a volatile word, and unfortunately has acquired the status (Urban) of instigating severe reactions. It is a crime, a serious felony, depending on INTENT. A Board projecting profit lines for the next quarter with proprietary data are 'conspiring' to succeed.

INTENT is perhaps the squishiest word on the Planet, yet the basis for virtually all of our Law. If the plan is to avoid or circumvent the regulations it may be borderline chargeable. If it is blatant, void of consideration of "Duty of Care", it may be criminal.

Hunched together at either end of the spectrum, nothing is gained, certainly not progress, by expecting great loads of intelligent thought to disappear upon the utterance of a word.

It is a tactic, nothing more.

bear
 
Old 26th May 2011, 14:36
  #2448 (permalink)  
 
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Hi Bear,
Originally Posted by bearfoil
It is a tactic, nothing more."
Well, I've also read a few late posts from you in the R&N thread where you mentioned (as a fact) that AF447 lost also Inertial References (horizon, attitude, etc.).
Hence, as your high morale stance may be sincerly doubted and those garbagistic uterly farcicalious numerous posts in the vein of the above are suggesting to me is that you are simply using your own proved "tactic, nothing more".
"Diffame, diffame, et diffame encore... il en restera toujours quelque chose d'utile à la fin !"
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Old 26th May 2011, 14:40
  #2449 (permalink)  
 
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takata, #2437

Sorry, but I didn't get any feeling of "conspiracy" from any part of the post you were discussing, or any problem with the translation. The point of it, afaics, was to illustrate that the problem is real and has been known about for quite a long time. If we clear away the bs, politics, bean counting, weasel words and excuses, we are still left with a failing that can have serious consequences.

If you think that this is not the case, then please explain...

Regards,

Chris
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Old 26th May 2011, 14:44
  #2450 (permalink)  
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Last dance and philosophy

Salute all!

A huge attaboy for the post by Sv concerning philosophy.

This shall be my last post on the matter until we all dissect the AF/BEA/Airbus folks' interpretation of the accident. I also thank all here for their nice comments ( a degree of acceptance amongst a group of "heavy" pilots, although I never flew a "heavy") and hope I have added to a technical understanding of FBW designs, design philosophy and corrections to both design and pilot procedures when unexpected situations are encountered that the design folks or pilots had not allowed for, however remote.

This is what got my attention from Sv:

Ultimate authority cannot be separated from ultimate responsibilty.

The only difference is not in numbers but in philosophy. As a passenger, I can entrust my life to someone who puts his own life on the line with mine. I can accept responsibilty and pay the ultimate price if I fail to deliver that promise as a pilot. But I will not accept to play scapegoat for a system that claims to be safer than I am when it is easy, and that evades responsibility when things go wrong.
That quote embodies the most profound thoughts I have seen on this topic. In short, rules to live by.

I am a "dinosaur" according to many. But I am an enlightened dinosaur. I moved up through the technological improvements in our jets gladly. I accepted the new capabilities and the new limitations on my superior aviating skills, heh heh. Most of all, I got to see problems and solutions along the way. Neither the pilots nor the designers were perfect. But both groups admitted it, and we sought and implemented solutions to prevent future accidents and to "improve" aircraft capabilities.

The last thing we did was tell the designers we didn't know that their jet could enter into an unrecoverable deep stall. The designers didn't tell us, "well, Gums, what in the hell were you thinking pointing the nose up at 80 degrees and not pulling down before the airspeed go too slow for the elevators to work?".

Later, when we found that our quad-redundant flight control computers and sensors went off-line due to a single-point-failure in the power supply system, we were livid!!! At the interim accident briefing our Wing CO came outta his seat and we had to hold him back before he punched out the GD briefer. Did the GD folks balk? No, they developed a better power supply system and we flew with a kludge, hot-wired-to-aircraft battery system for a year or so.

I don't see this with the Airbus folks. Sorry. I also do not comprehend an aircraft designed to fly at the "edge of the envelope" or all bets are off and we hand off the plane to the crew. Hal says, " I do not understand what is happening, Dave, you have the stick", GASP!

Last edited by gums; 26th May 2011 at 15:08.
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Old 26th May 2011, 15:03
  #2451 (permalink)  
 
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Instead of the swiss cheese model, bear, may I suggest "the links in the mishap chain" as a supplement. This model I was familiar with before the cheese model. It tends to indicate a serial order of causes and contributions to a mishap. Any one of these links being broken ends the accident event chain, and the mishap doesn't occur.

TEXT EDITED OUT, 3holelover covered this more concisely. LW50

"It's not the pitot tubes" is most likely right from an analytical sense, since pitot tube malfunctions are neither unknown nor new. You then trip over two systems interface issues: one is hardware to hardware, the other is hardware to wetware. (wetware ~ human brain) Since such issues can get quite complex, the easy soundbyte isn't available ... but giving out an uncomplicated soundbyte is what is asked for in the public information sector of the process.

Were no rice bowls at risk of being tipped, you'd get a different (and cleaner) analytic approach from parties A, B, C, D, etcetera, and different PR emissions.

Last edited by Lonewolf_50; 26th May 2011 at 15:18.
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Old 26th May 2011, 15:07
  #2452 (permalink)  
 
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one expects a little slack. [....] by now, don't we know what we mean ?
Yessir. True enough. I'll offer my humble apologies, and lots of slack... and shut up now.
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Old 26th May 2011, 15:10
  #2453 (permalink)  
 
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As a passenger, I can entrust my life to someone who puts his own life on the line with mine.
As a fare paying passenger I want to know that you are doing exactly as required by the regulations and that you have taken all reasonable care to ensure that I arrive in one piece at my destination. I do not want a chancer up front.

Computer easily wins if given a choice because humans are more fallible. Simple statistical fact.

f you view an accident as a series of links in a chain, or a series of holes in slices of cheese - whichever one prefers - surely the elimination of any link, or hole, is a valuable goal.
Most sensible comment since the beginning of the thread.

jcjeant you are getting boring. Air France had every opportunity to replace the probes just like everyone else. The fact they questioned it and left it very late before replacing, apparently to save money, says more about Air France than Airbus, Thales or Goodrich.

The A330 is a mighty fine aircraft. Pilots will never match the computers and its pretty blinkered to think you can. Safety statistics have never been better. Even if the software pitched the aircraft up in this case and I say IF, there was still no guarantee that this aircraft would have been saved.

I remind you all of the analogue 757 that lost its speed indications, the Birginair 757 that had ONE blocked tube.

Think about it.
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Old 26th May 2011, 15:17
  #2454 (permalink)  
 
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“Nowadays, at some airlines, an instructor or examiner will slap your hand if you choose to fly manually during some parts of a sim check. It is forbidden to touch the manual pitch trim of any Airbus if it is not flying in Direct Law, which never happens in the sim, except for one minute and a half upon initial training so the appropriate box can be ticked.”
On any specific FFS IOS Malfunction page under FLIGHT CONTROLS, you can count more than 20 selectable icons and under ADIRU, you can count more than 10.

In both B & A simulators, you see numbers of malfunctions available which are not incorporated in any training syllabus and are thus never utilized. (“Only move the shiny switches.”)

I realize there is a certain basic common default package, however.
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Old 26th May 2011, 15:19
  #2455 (permalink)  
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3holelover

Sorry if I was a little too assertive there, but Lonewolf and you have given me a thought.

I think honestly that what I see with the cheese is metaphoria. It is not helpful to simplify with homily a serious safety discussion. I am pedantic here, but sometimes.....

Cheese emphasizes the randomness of this outcome, and it was not random, I'll bet my Calloway. It was predictable, borderline inevitable, and I think that is where Svarin and PJ2 are taking us all. It was a block, no a loaf, of cheese, with one void only, impossible to misalign.

If 447 wandered into Scratch's cave, that is a bad thing, throw in Ice, more bad, virtually any "mitigating" excuse is just that, an excuse. I smell some corporate nonchalance, here, will it be reinforced tomorrow? Defended?
 
Old 26th May 2011, 15:23
  #2456 (permalink)  
 
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bear, my love of links (golf or sausage) aside, the variables interact with each other in dynamic systems. (Such as the case under consideration).

I think you are being reductionist with your block of sharp cheddar.

I believe the BEA will not be reductionist.
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Old 26th May 2011, 15:27
  #2457 (permalink)  
 
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Cool

Hi,

go ahead but you should certainly include the source where it comes from.
No probs ..
Les dossiers noirs du transport aérien
it's from one of the expert (member) of this family association
Bienvenue sur le site de l'association entraide et solidarité vol AF447
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Old 26th May 2011, 15:28
  #2458 (permalink)  
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Lonewolf

"...
bear, my love of links (golf or sausage) aside, the variables interact with each other in dynamic systems. (Such as the case under consideration)..."

Of course, and my post was simplistic. Millions of people are going to be assaulted with reductionist rhetoric tomorrow, from all sides. After 38 logged events, one believes the pile of Swiss is getting a bit rangy. A causal chain becomes a necklace after enough iterations.
 
Old 26th May 2011, 15:39
  #2459 (permalink)  
 
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Hi Chris,
Originally Posted by syseng68k
If you think that this is not the case, then please explain...
My main concern with jcjeant's post is that it is posted from a source which is not quoted at the first place. (Now, it is also translated with meaningless sentences). Anyway, I know that it is taken from a place where you can only find a compilation of documents (duely commentented) aimed at charging Airbus for its so many so-called wrong doings. There is nothing objective in such compilation as any communication on safety issues can be freely used as a proof of what they are suggesting: they did nothing and everything was aimed at discharging the manufacturer in case of trouble.

I myself posted about it, saying that it was a long story with Airbus "probe issues" (including the part of the manual dated from December 1999 explaining how to indentify unreliable air data).

Nonetheless, the way this issue is presented and commented is completely misleading:
Fact #1: Airbus did certainly something when the first issues appeared with Goodrich/ Rosemount P/N 0851GR which was the original probe on A330 (and issues were quite different from today context)... they developped with Goodrich the P/N 0851HL (not the Thales/Sextant C16195AA and later BA).
Fact#2: They worked on systems like the BUSS (Back-Up Speed System) and invested further in R&D technology ([email protected] probes, etc.).
Fact#3: Emphasis was also put on the crew training for detecting any possible Air data issues ; the fact is that possible Air data issues must be, in any case, monitored in flight because there is plenty of different cases following various "contaminations" of an anemometric chain. This is not a single case issue with a single procedure to follow as it is too complex to indentify correctly what is causing those Air data to be unreliable at the first place.

Now, it may appear that the weakest link was the last one and we'll see that tomorow. From what I have read on the crew training by Air France, they were simply not drilled at tackling this situation at cruise level: a single training was made months ago about another critical situation (UAS in approach or landing phase), but here, there was no switch to Alternate Law and the basic reaction would have to be quite different in this case, with much more thinking (and time) about what to do before altering their flight parameters (possibly safe when this event started).
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Old 26th May 2011, 16:22
  #2460 (permalink)  
 
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The real philosophical question faced today by passengers is whether they would entrust their lives to a (very well-trained) human pilot (who will share their fate), or to a (very well-designed) computer.
I never quite understood why this has to be a choice. It seems to me that future systems will need to seriously consider a solution where the pilot and the computer work together if we need to see improvements (in safety and other areas) in an already extremely safe system (as you pointed out in your earlier post).

But I will not accept to play scapegoat for a system that claims to be safer than I am when it is easy, and that evades responsibility when things go wrong.
I would replace when it is easy with when things work, because, that is by definition, what makes FBW flight safer than purely human operated flight. Realistically, we (as pilots) don't know anything about the hairy situations that were successfully negotiated by computers. And somewhere in there lies the paradox setup by the false dilemma of "either computer or human" type thinking.
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